Composite brake-shoe.



Nn. 618,139- named my 9, lem. l?k R. SPEAR.

GQPQSITE BRAKE SHOE.

(Application lnd (Ich.v 29, 1900.)

(No Modal.)

UNITED STATES vPATENT OFFICE.

FRANK R. SPEAR, OF CHICAGO, ILLINOIS.

COMPOSITE BRAKE-SHOE.

SPECIFICATION forming part of Letters Batent No. 678,139, dated J' uly 9, 1901.

Application ilecl October 29, 1900.

To a/ZZ whom t may concern:

Be it known that I, FRANK R. SPEAR, of Chicago, Illinois, have invented certain new anduseful Improvementsin CompositeBrake- Shoes, of which the following is a specication.

My invention has for its object to produce a composite brake-shoe in which the wearingface is provided with a composition more durable and efficient than has been heretofore employed, to my knowledge, and this I secure by the employment of coal-tar or coal-tar pitch as the essential ingredient of my com position.

Composite brake-shoes have been patented, and many of them experimented with and used to a greater or less exten t,in which the wearin gface is provided with masses of compositions of Various ingredients, generally consisting, however, of some metallic substance in a state of fine mechanical division in conjunction with a binder, such as asphaltum and the like. The chief trouble which has occurred heretofore in the use of brake-shoes having compositions of this character has been that the composition is subject to disintegration in service and soon falls out of the pocket or cavity formed in the shell or shoe. This disintegration is probably due to the excessive heat generated by the extreme pressure of the brake-shoe upon the wheel, this extreme pressure, particularly at a high rate of speed, being sufficiently great to generate a low red heat.

I employ as the chief ingredient of the composition the residuum of destructive distillation of coal-for example, in the production of coke and coal-gasA-which residuum is a thick viscid substance commonly known as coaltar. This coal-tar I prefer to employ in the more refined condition, which is brought about by removing therefrom some of its constituents, such as the analin colors, in which more refined condition it is known as coaltar pitch. I have found that either of these substances,or-,inotherwords,this substancein either condition above described, when mixed with some of a number of well-known ingredients commonly used for this purpose, will give a superior composition for use in brakeshoes. The other ingredients which I prefer Serial No. 34,747. (No specimens.)

to employ are asbestos and iron-borings or iron-filings.

My composition may be composed of these several ingredients in the following proportions: iron-borings, two hundred pounds; asbestos, twenty-five pounds, and coal-tar or coal-tar pitch, twenty-live pounds. In compounding these ingredients the asbestos in the fibrous form is mixed with the iron-borings, and the coal or coal-tar pitch is heated and added to the mixture. The mass is thoroughly worked, and while it is still'hot it is charged into the pockets or cavities of the shell of the brake-shoe under suitable pressure, where it solidiiies quickly.

In the accompanying drawings is shown a brake-shoe of the general class or kind to which my invention applies.

Figure lis a face or plan view; Fig. 2, a side elevation, and Fig. 3 a cross-section.

The body or shell of the shoe is marked A,

and it has one or more pockets'or recesses in its face, the cross-sectional form of the pocket or recess preferably being dovetailed. B rep- 'resents the composition mass within such pocket.

The form of the brake-shoe is immaterial,

and the form of the recesses or pockets may be varied at pleasure.

In use I have found that this composition does not disintegrate under any heat produced by the friction of the shoe upon the car-wheel. Coal-tar or coal-tar pitch not only acts as a binder in mixing the composition, but under the action of the heat due to friction it apparently is not affected throughout the mass, but only upon the surface, and such surface under theinfiuence of the heat and pressure becomes hard and glossy, but to the touch appears to possess in low degree the quality of lubrication. It does not under' heat and pressure become fluid or even plastic, but particles in the form of soot may be removed from the surface after it has been subjected to use. the composition does not become heated throughout, and lit is to this' characteristic that I attribute the lasting quality of the material, since the major portion of the mass ap parently is unaffected by service and is only Tests have shown that the mass of 95 IOO worn as the Wear on the face of the shoe progresses. I have found this composition to possess the requisite frictiona-l qualities in high degree. Y V IVhileI have indicated a composition containing certain ingredients, I do not intend to limit my invention to the described ingredients nor to the exact proportions stated. The qualities and the purpose of using the; iron-borings and asbestos are Well known and one or both of them may be omitted, provided that other substances be substituted serving, the same or substantially the same purposes in the composition. For example, the asbestos may be substituted by some other ingre-Y dient of a fibrous nature having the property of binding the mass together and preferably capable of resisting Wear, and the iron particles may be any form of that metal in a n'e state of division, or other metal in like state may be employed.

One result of the Wear of the composition due to the friction, which is highlyimportant, is the coating of the Wheel-surface with a skin of the material of the composition itself, and as the composition wears down the suvrg face of the mass gives off a tine substance in l a form which is most nearly described by the l term soot, being a fine powder having ant adhesive quality, and this ne adhesive powder Will coat the metal surface of the shoel and the Wheel-rim, and this coating protects l 4and `to the rail. `danger of the occurrence of this interlocking themwheel and shoe in their Contact with each other, and also protects the Wheel in its contact with the rail and minimizes the Wear of the Wheel to an appreciable extent.

While I have described the detritus produced by Wear as having a lubricating quality, it will be understood that said quality does not detract from the efficiency of the shoe to produce braking friction upon the Wheel, but, on the contrary, it materially adds thereto. The lubricating quality of the composition is also such as to prevent the locking of the shoe to the Wheel under excessive pressure, as in making an emergency stop.l It is well known that brake-shoes are sometimes forced into Contact with the Wheel under such pressure as to positively lock the surfaces together, thereby causing the sliding of the Wheels, which is destructive alike to the Wheel My composition reduces the of the shoe and wheel to a minimum.

,I claiml. A composition for brake-shoes having as an essential ingredient coal-tar or `coal-tar pitch, iinely-divided particles of metal and a fibrous substance, substantially as described.

2. A composition for brake-shoes composed essentially of comminuted iron, asbestos and coal-tar, substantially as described.

FRANK R. SPEAR.

I lVitnesses:

C. C. LINTHICUM, ADA H. BARNES. 

